About Question enthuware.oce-jpad.v6.2.492 :

[ETS User]

I need somebody to confirm that answer D is legitimate.

select count(s.presentations) from Student s
(Assume that presentations is a Collection field in Student)

If s.presentations is collection, you can't put use it as an argument for count operation, you'd have to join first with presentation, like so:

select count (p)
from Student s left join s.presentations p

[admin]

count(s.presentations) is valid even without a join. You may want to run the sample application verify this. You can get the sample application from: http://enthuware.com/index.php/mock-exa ... oce-jpa/85

HTH,
Paul.

[Guest]

count(s.presentations) is valid even without a join. You may want to run the sample application verify this. You can get the sample application from: http://enthuware.com/index.php/mock-exa ... oce-jpa/85

HTH,
Paul.

I rechecked using your test application and I still don't see how it can work. It fails in the test application also:

Code: Select all

select count(p) from Student s join s.presentations p 

returns properly:

Code: Select all

JPA Query Output - 
[ArrayList Size=1
  [Long : 5]
]

but

Code: Select all

select count(s.presentations) from Student s

does not allow this:

Code: Select all

Exception :org.hibernate.exception.SQLGrammarException: Syntax error: Encountered "." at line 1, column 14.

[admin]

May be I am misinterpreting something but as per section 4.8.5:

For all aggregate functions except COUNT, the path expression that is the argument to the aggregate
function must terminate in a state field. The path expression argument to COUNT may terminate in
either a state field or a association field, or the argument to COUNT may be an identification variable.

In this case, s.presentation is an association field, so it should work.
But you are right it doesn't work in the test application either.

I am really sorry about the wrong information.

-Paul.

[cosminvacaroiu]

size would work instead of count

[cosminvacaroiu]

a association field may be single-valued or collection-valued. So it's single-valued (a single entity).
You can't put max(someEntity).
It doesn't work with collections The only 2 functions/expressions that work with collection-valued associations are: SIZE & IS EMPTY, which will generate subqueries, which might be confusing, I don't understand why they even put these 2.

Cheers.

[javakid]

According the discuss above, it seems like the option D is correct.
I have written codes to confirm that count() with collection field is valid.
I thought the correct answer will be 4 options.
Would anyone tell me why option D is not included in the correct answer?
Thanks.

[ikotev]

Hello I also can confirm written above. Will someone update the question bank and include answer D as correct.

[admin]

Updated.
thank you for your feedback!